Method of reinforcing concrete floors and the like, and a reinforcing element therefor



Feb. 7, 1967 SVEN-ERIK BJERKING 3,302,360 METHOD OF REINFORCING CONCRETEFLOORS AND THE LIKE, AND

A REINFORCING ELEMENT THEREFOR Fiied Dec 23, 1963 4 Sheets-Sheet 1 Fig.1

Feb. 7, 1967 SVEN-ERIK BJERKING 3,302,360 METHOD OF REINFORCING CONCRETEFLOORS AND THE LIKE, AND

A REINFORCING ELEMENT THEREFOR Filed Dec. 25. 1963 4 Sheets-Sheet 2-Filed Dec. 23, 1963 eb. 7, 1967 SVEN-ERIK BJERKING 3,302,360

MIL'TIIOD OF REINFORCING CONCRETE FLOORS AND THE LIKE, AND

A REINFORCING ELEMENT THEREFOR 4 Sheets-Shet (5 7, 1967 SVEN'ERIK BJERKmG 3,302,360

METHOD OF REINFORCING CONCRETE FLOORS AND THE LIKE, AND

A REINFORCING ELEMENT THEREFOR Filed Dec. 25, 1963 4 Sheets-Sheet 4United States Patent 3,302,360 METHOD OF REINFORCING CONCRETE FLOORS ANDTHE LIKE, AND A REINFORCING ELE- MENT THEREFOR Sven-Erik Bjerking,Gotgatan 3, Uppsala, Sweden Filed Dec. 23, 1963, Ser. No. 332,447 Claimspriority, application Sweden, Jan. 9, 1963, 214/63 12 Claims. (Cl.52-600) As is well known, concrete floors and other substantiallyhorizontally extending, self-supporting concrete structures are providedboth with a bottom reinforcement which, in the case of floors, isconstituted, as a rule, by a grid of crossing reinforcing bars extendingthroughout the free length and width, respectively, of the floor andspaced slightly above the bottom surface of the slab, and with aso-called top reinforcement disposed adjacent and above supportingwalls, supporting columns or other supporting points and consisting ofcomparatively short reinforcing bars which are embedded in the concretea few centimeters beneath its free top surface. The bottom reinforcementis usually placed on thin concrete spacer blocks which rest on the mouldbottom and support the reinforcement bars at a desired level above thesame. It is the usual practice to place the top reinforcement on aplurality of cross-wise extending, relatively thick reinforcement irons,s-o-called mounting irons, which are supported, in turn, by spacermembers of the required rather considerable height placed on the bottomreinforcement and usually consisting of reinforcement irons bent into asuitable shape.

The mounting irons and the appertaining spacer members have for theirsole purpose to maintain the top reinforcement in proper position duringthe casting operation, and they do not increase the load-carryingcapacity of the finished concrete slab or the like. It has long beenfelt to involve a waste of reinforcing steel to use heavy, transverselyextending mounting-steel members supported on separate, relatively highsupports for the single purpose of keeping the top reinforcement inposition during the casting operation. Further, it has been experiencedthat the mounting irons supported at a substantial height above themould bottom are in the way of the worker who may readily stumble overthe irons as he must pass over the same. Therefore, it has long beendesired to find another, more practical and economical solution to theproblem of keeping the top reinforcement in place during theconcrete-casting operation.

In accordance with the invention this problem has been solved byproviding special top reinforcement members by bending lengths ofreinforcement-steel at their ends, and possibly also intermediate theirends, so as to form a kind of feet which, supported on the bottomreinforcement or on low supporting blocks of concrete or the like placedon the mould bottom, maintain said reinforcement members at a desiredlevel above the mould bottom. According to the invention, these feet areprovided by bending a reinforcement steel into the shape of a preferablyclosed and substantially rectangular, elongate stirrup, or loop, and bybending off one end portion, at least, of this loop through a suitableangle from the plane common to the two longitudinally extendingportionsthereof, and in a manner to cause the supporting surfaces on thebent-off portions to be disposed at such a distance from the planecommon to the two longitudinally extending portions that, within theconcrete structure to be cast, the latter will be disposed at a desireddepth beneath the free top surface of this construction.

It has been found by accurate testing that the bentoff end portions ofthe reinforcement-steel members are adapted to ensure an excellentanchorage of these 'steel 3,302,360 Patented Feb. 7, 1967 members attheir ends within the concrete, making it unnecessary to extend thesteel members lengthwise in order to ensure sufficient gripping action.In other words, the bent-off end or foot portions will not, or will onlyunnoticeably, increase the required weight of the reinforcing members ofthe top or topedge reinforcement, and in certain cases it would even bepossible to count upon a reduction of the required steel weight. Theelimination of mounting iron and the high supports therefor involve acorresponding direct saving in steel weight, since, as mentionedhereinbefore, these elements do not contribute to the strength of thefiinished concrete slab or the like. It has been found that, by applyingthe invention to the top reinforcement of concrete floors, it ispossible to reduce the weight of steel for the top reinforcement by noless than up to 30% to 40%. In addition, the elimination of theobstructive mounting irons and high supports will render the mounting ofthe top reinforcement more convenient and less dangerous, because theworkers can now walk unobstructedly on the bottom reinforcement. Furtherthere will be no exposed sharp ends of concrete steel projecting upwardsto a dangerous height above the mould bottom likely to cause injury tothe worker or damage to his clothes.

The invention will now be described more in detail with reference to theaccompanying drawings, in which:

FIGURE 1 shows a plurality of concrete-reinforcing elements according tothe invention in the form of closed elongate loops bent-off or angularlyoff-set at both ends, and supported upon the bottom reinforcement for aconcrete floor above an intermediate supporting or spine wall;

FIGURE 2, in a similar manner, shows the disposition of reinforcingelements in the form of open loops;

FIGURES 3 and 4 illustrate two different ways of forming a topreinforcement comprising reinforcing elements disposed in pairs ofelements overlapping each other endwise;

FIGURE 5 shows reinforcing elements formed with intermediate supports orfeet and disposed in place in the casting mould;

FIGURES 6 to 10 show further applications of the invention.

Referring now to FIGURE 1, numeral 10 designates the mould for casting aconcrete floor, numeral 11 denotes a supporting or spine wall which hasjust been cast and is intended to support the concrete floor, and 12designates the bottom reinforcement. The latter, conventionally,comprises longitudinally extending reinforcing-steel bars 13 andtransversely extending reinforcing-steel bars 14 crossing the bars 13.The bottom reinforcement is supported on low concrete spacers 15 whichare disposed on the mould bottom, whereby a predetermined clearance ismaintained between the bottom reinforcement and the mould bottom.

The top reinforcement comprises a plurality of reinforcing elements 16formed in accordance with the present invention and disposed inside-by-side relation upon the bottom reinforcement 12. Each reinforcingelement consists of a reinforcing-steel bar which is bent into the shapeof a closed elongate rectangular loop which, in its turn, is bent off atits ends whereby the short transverse end portions 17 of the rectanglewill form feet for carrying the long portions 18 extendinglongitudinally. The reinforcing elements are placed on the bottomreinforcement with its foot portions 17 supported on corresponding onesof the transversely extending reinforcing bars 14. The feet 17 are tiedto the reinforcing bars with tie wires or lashings 19 whereby thereinforcing elements are securely maintained in predetermined positionsrelative to the bottom reinforcement. The distance of the bent-off footportions 17 from the common plane of the longitudinally extend- 3 ingportions 18 is so chosen in relation to the thickness of the concretefloor to be cast as to cause the longitudinally extending portions to bedisposed at a desired depth beneath the top surface of the finally castfloor.

The bent-off end portions will afford for the reinforcing elementsaccording to the invention an extraordinarily satisfactory anchoragewithin the concrete, and this renders it unnecessary to extend thelongitudinal portions-- which will have to carry the tensile andcompressive loads concerned further in order to ensure the requiredgripping action at their ends. This means that, to obtain a givenreinforcing effect, the straight longitudinal portions can be made of alength which is so much shorter than that of conventional straightreinforcing :bars that the overall weight of the reinforcing elementwill scarely be higher, and in certain cases even lower, than the weightof two straight reinforcing bars of the same cross-sectional area. Inaddition, the omission of high supports and mounting members, therefore,as a rule, will involve a direct saving in overall steel-weight.

In the embodiment of FIGURE 1 the butt ends of the reinforcing steel barbent into a rectangular loop are assumed to be joined together, such asby a butt weld 20, whereby each reinforcing element will form asubstantially rigid unit with no pointed portions which could causeinjury to the worker. However, the ends directed towards each other neednot necessarily be joined together, and, in fact, need not actually meeteither.

The spaced parallel parts of the bent-off end portions suitably formobtuse angles with the longitudinal sides of the reinforcing element,these angles being preferably about 120. When forming the elements inthis way, it is possible to tie together a plurality of reinforcingelements into bundles which are easily handle which is a great advantagewhen manufacturing the elements in quantities. This configuration, inaddition, will increase the resiliency of the reinforcing element,whereby it will be capable of reverting to its initial shape aftersubjecting the straight sides to moderate loading forces.

FIGURE 2 illustrates a modified configuration of the reinforcing elementaccording to the invention. In this case, the element has the shape ofan open loop bent off at its closed end into a transverse foot 17, whilethe free ends of the loop are bent downwards and backwards to form twoseparate feet 21 extending in spaced parallel relation to thelongitudinal sides 18 of the reinforcing element. The feet 17 and 21 aretied to the bottom reinforcement.

The feet at the free ends of the loop, of course, can be formedotherwise than as shown in FIGURE 2, in that they may be bent away fromeach other, for example.

FIGURE 3 illustrates the possibility, in top-edge reinforcing a concreteslab above an intermediate supporting or spine wall, of using pairs ofrelatively overlapping, comparatively short reinforcing elements 16.FIGURE 4 illustrates a similar arrangement with reinforcing elementsoverlapping in pairs over a longer portion of the length of thelongitudinally extending sides.

FIGURE 5 shows reinforcing elements which, in addi tion to the bent-offfoot-portions 17 at their ends, are provided intermediate their endswith supports formed by bending each longitudinally extending rodportion 16 into an elongated loop 23 having its overlapping portions inclose proximity to each other.

FIGURE 6 illustrates a suitable disposition of the reinforcing elementsaccording to the invention adjacent to an external supporting wall, andFIGURES 7 and 8 show suitable arrangements thereof above a supportingcolumn.

FIGURE 9 shows a modified form of the reinforcing element of theinvention. This element, being in the shape of a closed rectangle, isbent off into a foot at one end of the rectangle only. The figureillustrates a plurality of such reinforcing elements disposed across thetop of a concrete joist to be cast integrally with the concrete floor.The reinforcement for this joist is indicated at 24. The

reinforcing elements of the invention are supported at their bent-offends on the bottom reinforcement (not shown) for the concrete-floor slabto be cast, whereas the elements are supported near their opposite endson the reinforcement for the joist.

FIGURE 10 shows a suitable disposition of reinforcing elements of thesame configuration as those of FIGURE 9 adjacent a construction joint inthe floor to be cast. The reinforcing elements are supported at theirstraight ends on a mould board 25 temporarily placed on an edge on themould bottom 10 and intended to be removed after the floor slab to theright of said board has been cast.

The invention is not limited to the embodiments illustrated in thedrawings and described in detail herein, but modifications areconceivable without departing from its scope.

What I claim is:

1. A method of reinforcing concrete floors and other substantiallyhorizontally-extending, self-supporting concrete structures, having anupper surface and a lower surface, comprising:

(a) disposing in the lower portion of said floor a plurality ofelongated straight steel rods;

(b) supporting said steel rods in a first horizontal plane above thelower surface of said floor to form bottom reinforcing means;

(c) disposing in said floor at least one rectangular, continuous, steelloop, having at least one end thereof bent downwardly to providevertically-disposed legs and a horizontal support foot of substantiallength formed by the end of the rectangle; and

(d) supporting said foot in a horizontal plane above said lower surfaceof said floor with said support foot essentially the same distance abovesaid lower surface of said floor as said bottom reinforcing means, andthe sides of said rectangle in a second horizontal plane above saidfirst horizontal plane and in the upper portion of said floor to formtop reinforcing means.

2. A method in accordance with claim 1 wherein both ends of the loopsare bent downwardly to form support feet.

3. A method in accordance with claim 1 wherein the foot of the loop issupported by and fastened to the rods.

4. In reinforced concrete floors and other substantiallyhorizontally-extending, self-supporting concrete structures, having anupper surface and a lower surface, the improvement comprising:

(a) a plurality of elongated, straight steel rods disposed in a firsthorizontal plane above said lower surface of said floor to form bottomreinforcing means;

(b) at least one rectangular, continuous steel loop, having at least oneend thereof bent downwardly to provide vertical legs and a horizontalsupport foot of substantial length formed by the end of the rectangle,disposed with said foot in a horizontal plane above said lower surfaceof said floor with said support foot essentially the same distance abovesaid lower surface as said first horizontal plane and the sides of saidrectangle in a second horizontal plane above said first horizontal planeand in the upper portion of said floor to form top reinforcing means;and

(c) spacer means in the bottom of said floor to temporarily support andspace said bars and said foot above said lower surface of said floor.

5. A structure in accordance with claim 4 wherein both ends of the loopare bent downwardly to form support feet.

6. A structure in accordance with claim 4 wherein the foot of theloop-is supported by and fastened to the rods. M

7. A structure in accordance with claim 6 which additionally includestie wires fastening the foot of the loop to the rods.

8. A reinforcing element for reinforcing the top of concrete floors andother substantially horizontally-extending, self-supporting concretestructure comprising: a rectangular, continuous steel loop ofsubstantial width, having at least one end thereof bent downwardly toprovide vertical legs and a support foot of substantial length formed bythe end of the rectangle, said support foot being in a plane parallel toand spaced from the plane of the sides of said rectangle.

9. A reinforcing element in accordance with claim 8 wherein at least onesecondary, vertically-disposed, rectangular loop is formed by a side ofsaid main loop and has a vertical height equal to the spacing betweenthe two parallel planes so that one side of the secondary loop is in oneplane and the other side of the secondary loop is in the other plane.

10. A reinforcing element in accordance with claim 8 wherein both endsof the rectangle are bent downwardly to form support feet.

11. A reinforcing element in accordance with claim 10 wherein the angleis 120.

12. A reinforcing element in accordance with claim 8 wherein legs forman obtuse angle with the sides of the loop.

References Cited by the Examiner UNITED STATES PATENTS 1,182,421 5/ 1916Ramsey 52-251 1,244,641 10/1917 Pratt 52251 1,335,780 4/1920 Barton52253 1,625,899 4/ 1927 Lally 52260 1,693,941 12/1928 Schuster 522612,140,313 12/ 1938 Dellenbarger et a1. 52-648 FOREIGN PATENTS 55,91410/1912 Austria.

FRANK L. ABBOTT, Primary Examiner.

20 J. L. RIDGILL, Assistant Examiner.

4. IN REINFORCED CONCRETE FLOORS AND OTHER SUBSTANTIALLYHORIZONTALLY-EXTENDING, SELF-SUPPORTING CONCRETE STRUCTURES, HAVING ANUPPER SURFACE AND A LOWER SURFACE, THE IMPROVEMENT COMPRISING: (A) APLURALITY OF ELONGATED, STRAIGHT STEEL RODS DISPOSED IN A FIRSTHORIZONTAL PLANE ABOVE SAID LOWER SURFACE OF SAID FLOOR TO FORM BOTTOMREINFORCING MEANS; (B) AT LEAST ONE RECTANGULAR, CONTINUOUS STEEL LOOP,HAVING AT LEAST ONE END THEREOF BENT DOWNWARDLY TO PROVIDE VERTICAL LEGSAND A HORIZONTAL SUPPORT FOOT OF SUBSTANTIAL LENGTH FORMED BY THE END OFTHE RECTANGLE, DISPOSED WITH SAID FOOT IN A HORIZONTAL PLANE ABOVE SAIDLOWER SURFACE OF SAID FLOOR WITH SAID SUPPORT FOOT ESSENTIALLY THE SAMEDISTANCE ABOVE SAID LOWER SURFACE AS SAID FIRST HORIZONTAL PLANE AND THESIDES OF SAID RECTANGLE IN A SECOND HORIZONTAL PLANE ABOVE SAID FIRSTHORIZONTAL PLANE AND IN THE UPPER PORTION OF SAID FLOOR TO FORM TOPREINFORCING MEANS; AND (C) SPACER MEANS IN THE BOTTOM OF SAID FLOOR TOTEMPORARILY SUPPORT AND SPACE SAID BARS AND SAID FOOT ABOVE SAID LOWERSURFACE OF SAID FLOOR.